Hydrocarbon conversion



' Patented Sept. 16, 1941 HYDROCARBON CONVERSION Don a. Carmody, Whiting, Ind., and Alex G. Oblad, Chicago, 111;, assignors to Standard Oil Company, Indiana Chicago, a

a corporation iif No Drawing. Application December 7, 1939,

Serial No. 308,046

8 Claims.

This invention relates to an improved process for the production of branched-chain hydrocarbons of high anti-knock value. More particularly, it relates to the -alkylation of iso-paraffinic hydrocarbons with organic chlorides.

It is an object of our invention to provide an improved process for the production of branchedchain hydrocarbons. Another object of our invention is to provide a process for the allgvlation of iso-paraffinic hydrocarbons with organic halides. A further object of our invention is to provide a process for the production of normally liquid hydrocarbons having high anti-knock value from normally gaseous hydrocarbons. A still further object of this invention is to provide a process for the utilization of methane in the production of high anti-knock motor fuels. Further objects and advantages will become apparent as the description of our invention pro-' oeeds.

Stated briefly, our process comprises the alkylation of an iso-paraflinic hydrocarbon with methyl chloride which has been prepared by the chlorination of methane. In the production of hydrocarbons of gasoline boiling range by the cracking of petroleum oils, varying amounts of normally gaseous hydrocarbons are obtained as a by-product. Until recent times these were considered as waste products and utilized chiefly as fuels with.

some slight use as refrigerants and solvents. It has now been recognized that these normally gaseous hydrocarbons are a valuable source of material for the production of high anti-knock motor fuels through such processes as polymerization and alkylation. However, these processes are directed chiefly to feed stocks comprising hydrocarbons having 3 and 4 carbon atoms per molecule although there have been successful attempts to include ethane and ethylene. In all cases, however, methane is discarded with the hydrogen since heretofore no satisfactory process has been devised for utilizing the methane in the production of high anti-knock fuels. Methane is also discarded from the gases obtained in natural gas or recycled to the underground formation so that the available amount of methane is enormous while its utilization in hydrogen synthesis hasnot achieved commercial success.

When employing polymerization or alkylation for the production of high anti-knock motor fuels from normally gaseous hydrocarbonsthe resulting hydrocarbons almost invariably contain six or more carbon atoms per molecule. While such products with, their highly branched configuration are desirable and valuable for premium fuels,

and particularly for aviation fuels, they are usually low in volatility. It is necessary, therefore, to blend with the fuels varying proportions of pentanes in order to increase the volatility. Since pentanes are also of the boiling range desirable by any one of a number of methods. For example, the production of methyl chloride thermally may be effected by passing a mixture of chlorine and an excess of methane through a reaction vessel at a temperature not exceeding 750 F. The reaction is aided to a considerable extent by the use of porous material such as animal charcoal, and vessels of quartz, porcelain, earthenware, etc. reduce the tendency forcarbon formation and separation. The time of contact should be of the order of about 10 seconds. It is usually desirable to have a considerable excess of methane, for example, 10 volumes of methane per volume of chlorine and to separate the products from the excess methane, which may be recycled.

Catalytically, methyl chloride may be prepared, for example, by passing a mixture of one volume of chlorine and two volumes of methane into molten potassium hydrogen sulfate at approximately 500 F. Again methyl chloride may be prepared by the treatment of a mixture of methane, hydrogen chloride and nitrogen at approximately 840 to 1200 F. in the presence of catalyst such as active carbon, cupric chloride, alkaline earth chlorides, etc. Numerous processes employing light energy in the form of sunlight, ultra .violet radiation, etc. have been used for the photo'- chemical chlorination of methane. The production of methyl chloride on a commercial scale with a good yield of product is entirely feasible.

The products of the chlorination under controlled conditions comprise chiefly chloromethane, although varying amounts of dichloromethane, chloroform and carbon tetrachloride may be formed. The products from chlorination may be separated by solidifying at subnormal temperaturesof the order of 185 F. to -20-F. under pressures up to atmospheres whereby the hydrogen chloride, methane and methyl chloride as well as any more highly chlorinated products are fractionally separated.

Methyl chloride produced by any of these methods is caused to react in accordance with our invention with a hydrocarbon having a tertiary carbon atom to form a branched-chain hydrocarbon having one additional methyl group as compared with the original hydrocarbon. Hydrogen chloride is formed as a by-product. It is particularly advantageous to alkylate isobutane with methyl chloride in order to obtain branchedinch, preferably at 2000 to 3000 pounds per square men. As catalysts for promoting the alkylation from and recycled to the chlorination step. The unconverted methane separated from the original chlorination step may be recycled with. the rewe may use compounds of metals selected from groups III, IV, V' and VI of the periodic table, particularly compounds of aluminum, boron, tin,

antimony, bismuth, arsenic, molybdenum, tungsten, titanium, thorium 'and zirconium. Of the compounds, we prefer to use the halides and particularly the chlorides. The halides of cerium, hafnium, colum'bium and tantalum may alsobe used. Iron chloride is also a suitable compound for use as a catalyst in our process.

In order to make our process commercially desirable it is advantageous to recover the chlorine from the hydrogen chloride produced in the alkylation and/or in the chlorination .of methane. This may be done by such processes as the Deacon process in which the hydrogen chloride is passed with air over a catalyst comprising cupric chloride, preferably on a support. The temperatures are of the general order "of 900 to 935 F. The

products comprisechiefly chlorine and water, with some unconverted hydrogen chloride and excess air.

The use of methyl chloride as an alkylating agent is particularly advantageous in that there are no side reactions involved, the methyl ,chloride reacting only with the isoparaflln present and not with itself. The contrary is true of organic chlorides such as ethyl chloride, etc. In

carrying out our process, methane from any suitable source such as the dry as from a cracking operation is converted to methyl chloride. The,

methyl chloride is separated from the uncon-' verted hydrocarbons and from the by-products of 'the reaction and is contacted with a butane cut comprising both normal and isobutanes but preferably free of unsaturates at- 400 F. and ata pressure of 2000 pounds per square inch over a catalyst consisting of aluminum chloride or double salts of metals of the first group with aluminum chloride, e. g., sodium chloroaluminate. If the latter catalyst is employed somewhat higher temperatures may be used. The products fromthe reaction step which are principally iso-- pentane or neopentane or a mixture thereof containing some hexanes resulting from double step alkylation are separated from unreacted butanes and the methylated isobutane washed to remove any entrained hydrogen chloride whereupon it is suitable for blending'with high octane number .a'viation fuels of low volatility. The hydrogen chloride fromv the alkylation step together with the hydrogen chloride formed in the chlorination step are directed, with air, to a recovery step wherein the products comprise chiefly free chlo rine and water; The chlorine is separated there- Our process is equally applicable to the alkylation of isoparafllnic hydrocarbons having more than 4 carbon atoms per molecule. For example, isopentane may be converted to dimethyl butane,

methyl pentane may be converted to dimethyl pentane, etc., the methyl group in all cases being added as a side chain to increase the branched configuration of the hydrocarbon.

. We claim:

1. A process for the production of a high octane number fuel comprising contacting a branchedchain parafflnic hydrocarbon with methyl chloride in the presence of a metallic halide alkylation catalyst under conditions adapted to promote the alkylation of sai ailiinic hydrocarbon with t said methyl chloride.

2. A process for the production of a high octane number fuel comprising contacting isobutane with methylchloride in the presence of a metallic halide alkylation catalyst under conditions adapted to promote the alkylation of said isobutane with the organic radical of said methyl chloride.

3. A process for the production of a high octane number fuel comprising chlorinating methane to methyl chloride and contacting at least one branched-chain parafiinic hydrocarbon with said methyl chloride in the presence of a metallic halide alkylation catalyst under conditions adapted to promote the alkylation of saidbranched organic radical of chain paraflinic hydrocarbon with the organic I number fuel comprising chlorinatingmethane to methyl chloride, reacting said methyl chloride with a branched-chain paraflinic hydrocarbon in the presence of a metallic halide alkylation catalyst under conditions of temperature and pressure adapted to promote the formation of a higher molecular weight hydrocarbon and hydrogen chloride, oxidizing said hydrogen chloride to recover chlorine therefrom and recycling said covered chlorine to the chlorination step.

I 5. A process according to claim 1 in metallic halide is a chloride.

6. A process according to claim lin whiclr a temperature within the range of-from 50 F. to 900 F. is employed.

7..A process according to claim 1 in which a pressure within the range of from 100 to 4500 pounds per square inch is employed.

8. A process according to claim 1 in which a 4 temperature within the range of from about F. to'400 F., and a pressure within the range of from about 2000 to 3000 pounds" per square inch is employed.

DON R; CARMODY.

ALEX G. OBLAD.

branched-chain parwhich the 

